Cathode ray tube apparatus



9 1939- K. SCHLESINGER 2,185,134

CATHODE RAY TUBE APPARATUS Filed Feb. 17, 1937 2 Sheets-Sheet 1 //7venta/-:

Dec. 26, 1939.

K. SCHLESINGER 2,185,134

CATHODE RAY TUBE APPARATUS Filed Feb. 17, 1937 2 Sheets-Sheet 2 (u) n '3' m 12 Patented Dec. 26, 1939 TE'l I cries STATES CATHODE RAY TUBE APPARATUS Application February 17, 1937, Serial No. 126,207 In Germany February 19, 1936 turns. The connection system in respect of Claims.

The invention relates to a method for the electrostatic-magnetic deflection of cathode rays, with the object to provide for the total deflection system {taking up merely a very small length, and of avoiding an influence of the two co-ordinates one upon the other.

The method is based on a principle disclosed in the co-pending United States Patent application Ser. No. 726,477, filed May 19, 1934, in

operating circuits, whereas Fig. 2 is a plan view from the screen side of the same tube, partly in section, and

Fig. 3 is a circuit diagram of the deflecting current supplying system.

Referring now to Fig. 1, the end of a metallic tube 1 is closed by a conical cover plate 2, which is situated opposite to a flat perforated plate 3. The arrangement 2 and 3 acts as an electrostatic lens immediately 3 possesses a higher potential than 2. At a distance 4, which is equal to or greater than three times the width of the inlet aperture of the deflecting condenser, there are situated the two deflecting plates 5 and 6. According to the invention, these plates consist of soft iron sheet having a coercive force as small as possible and a high permeability (transformer sheet iron). According to a further feature of the invention the plates are brought into contact with the outer wall 1 of the cathode ray tube by registers 8 and 9 which, according to yet a further feature of the invention, may conveniently consist themselves of a magnetically conductive material, such as iron or nickel. To produce a resiliency springs composed of sheet steel 10 may be welded, according to the invention, to the plates. Externally, on a level with these springs and registers, there is preferably placed about the tube, according to the invention, a sheet metal ring II, which in Fig. 2 is shown in cross-section Viewed from these windings is illustrated in Fig. 3. As well known, magnetic deflection of cathode rays is attended by the difliculty that a strong preliminary deflection is caused by the anode D. C. of the amplifying tube M. The coils, therefore, are usually fed over condensers, which, however, results in new difl'iculties arising from distortions in the form of the relaxation oscillations.-

According to the invention, the D. 0., in. the present arrangement,.is passed directly through one half-winding 53a, and traverses in series connection a second half-winding l3 provided for each coil. The two magnetic deflections of these coils are opposed to one another. Since the coils are traversed by the same current, no deflection will, therefore, occur in the state of rest. The alternating relaxation oscillation current, on the other hand, is passed only through the winding i312: and is prevented from entering the windings it by means of a condenser l5. A resistance !6 is provided, Which is selected so large (several thousand ohms) that no appreciable induced currents are able to flow in the circuit !5, l3, l6, [1. A

In this way increase in the self-induction of 13a is avoided. The complete sensitivity of deflection corresponding to the available relaxation oscillation A. C. flowing in the coil halves i3a is thus actually obtained.

The self-induction of the coils is so calculated that the tube l4 operates practically on shortcircuit. A pentode I4 is particularly to be recommended in order that the tube resistance will be large as compared with the impedance of the coils. The exciting potential at the grid of the pentode may be produced in the usual fashion by a relaxation oscillation circuit, comprising for example a charging resistance IS, a

v condenser 20 and a discharge tube l8, which may conveniently be a grid-controlled thermionic glow discharge tube having a suddenly changing characteristic.

The condenser I5 requires to be so large that its resistance is small as compared with the A. C. resistance of the coil l3a. In the case of relaxation oscillation frequencies of between 20 and cycles per second capacities of 10 to 20 mi. are suflicient.

50 above. Two pole pieces l2, which likewise con- The pair of deflecting Plates 5 and 5 Sh wn sist of a sheet metal of good magnetic conducin p Vi in 2 s be S e as co tivity, project towards the body of the tube and pared with the movement of the ray that over carry deflecting coils I3, l3a. Each of these the entire movement of the ray the field may be coils consists of two windings, which are conregarded as homogeneous and orthogonal. To

nected in series and have the same number of increase the sensitivity of the electrostatic deflection it is advisable to construct the plates 5 and 6 in plano-parallel form for long one-third of their length and then to bend them apart, e. g. as shown. The deflecting plates are preferably operated in reverse phase, as in this case the requisite spacing 4 is at its smallest. The overall length then amounts only to approximately 4 cm. (spacing 4:20 mm., height of plates=20 mm.). The luminous screen 2! may accordingly be approached into close proximity of the anode 3, which means a very small lens to image spacing resulting in fine points which is particularly desirable in the case of television projection tubes. Between the projection screen 2| and a ring 22, which latter is connected with the anode 3, there may conveniently be provided an after-acceleration produced by a spiral 23 of poor conductivity. The appertaining voltage is provided for by means of a mains apparatus, e. g., comprising, as shown, a condenser 24, a rectifying tube 25 and a high tension transformer 26, and is applied between the commencement and the end of the acceleration spiral 23. These tubes combine a faultless rectangular line screen with very intense and sharp image points due to the shortness of the distance between anode and luminous screen, which intense and sharp image points result, on a small image area, in an image which, in conjunction with a lens, permits of a good utilisation of the fluorescent light.

Further, according to the invention, cathode beam deflecting means may be provided wherein the magnetic flux is conducted through thin metal sheets of good magnetic conductivity or through one or more cores or pole pieces of compressed magnetic powder material. The cathode beam deflecting means may comprise magnet cores or pole pieces having insulating supports and finely pulverized magnetic carrying metals such as ferro-carbonyl powder on said support or having an iron-nickel aluminum alloy or an iron-nickel-copper alloy as magnetic material. The cathode beam deflecting means may comprise minute magnetic particles of elongated form which are preferably preliminarily directioned magnetically.

I claim:

1. Magnetic cathode ray deflecting means comprising means for producing an electric current having a direct current component and an alternating current component, a magnet coil system connected to said current producing means to be traversed by the mentioned electric current, said coil system comprising two coils connected in series and having about equal numbers of turns, the turns of said two coils being wound about a common axis in opposite directions, and means connected to the common connection of said two coils for by-passing the alternating current component of the mentioned electric current.

2. Magnetic cathode ray deflecting means comprising means for producing an electric current having a direct current component and an alternating current component, a magnet coil system connected to said current producing means to be traversed by the mentioned electric current, said coil system comprising two coils connected in series and having about equal numbers of turns, the turns of said two coils being wound about a common axis in opposite directions, and a condenser connected to the common connection of said two coils for by-passing the alternating current component of the mentioned electric current, said condenser having an impedance which is small as compared with the impedance of said coils.

3. The invention set forth in claim 1, and wherein said means for producing an electric current comprise an amplifier tube, the inner resistance of which is large as compared with the impedance of said magnet coil system.

4. The invention set forth in claim 1, and wherein said means for producing an electric current comprise an amplifier pentode, the inner resistance of which is large as compared with the impedance of said magnet coil system.

5..The invention set forth in claim 1, and wherein each of said two coils consist of two halves mounted at opposite sides of the normal path of the cathode ray to be deflected.

KURT SCHLESINGER. 

